Speaking as someone who is planning to write in the future - by which I mean "Edit a short story tomorrow," "Launch a Kickstarter for a novel next week," and "Participate in NaNoWriMo for the eighth or so time next month" - I can highly recommend On Writing. It's one of the very few books, out of easily a hundred or two, that I first had shipped up when I moved out of state. I'm sitting across from it even now.

Speaking of the Kickstarter: http://planetoz.net. I'm posting a writing tutorial link to the mailing list soon!